The present invention relates to printed circuit assemblies and more particularly to a method of bonding a surface of the dielectric substrate to a surface of the metallic carrier of a printed circuit assembly.
In the past it has been the practice of plating the surface of the substrate to be bonded to a surface of the carrier with a metal and then tinning both of these surfaces separately with solder. The tinned surfaces are separately cleaned to clean both of the tinned surfaces. A flux is applied to both of the cleaned tinned surfaces separately and both of the fluxed cleaned tinned surfaces are placed in contact with each other. Heat and pressure is then simultaneously applied to both of the substrate and the carrier until the solder of both of the fluxed cleaned tinned surfaces flows. Both of the bodies are then allowed to cool in a natural manner to room temperature while still applying the pressure to bond the substrate to the carrier.
A disadvantage of this method of bonding a substrate to a carrier in printed circuit assemblies is that intimate contact between the bonded surfaces may not be achieved due to trapped flux and additionally excess solder will flow out onto undesirable areas of the substrate and carrier, such as the outer surface of the substrate and the carrier adjacent the bonded joint.